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There are almost twice as many endangered green sea turtles swallowing plastic than were 25 years ago, according to an Australia study.
The debris they ingest includes plastic bags and bits of plastic milk and drink bottles, plastic buckets and containers. High density polyethylene is the most commonly ingested polymer.
The findings, based on data collected in 37 worldwide studies from 1985 to 2012, were analyzed by researchers at the University of Queens¬land in Brisbane and in a paper published in the journal Conservation Biology.
Study leader and doctoral candidate Qamar Schuyler said the number of green turtles ingesting debris jumped from 30 percent in 1985 to 50 percent in 2012.
The cause of death was unclear in most cases, but plastic products eaten by turtles and other marine life can be lethal. Schuyler said she suspects some died from plastic blocking their stomachs and starving them or puncturing their intestinal systems.
The ingested plastics can also release toxins into the turtles, which can grow to 5 feet long and live for 80 years.
Other turtles, such as more common leatherbacks, have also been found to have ingested plastic material.
Schuyler, originally from Seattle and studying in Australia since 2006, said the turtles' ages and size are also factors.
"Younger oceangoing turtles tend to eat smaller pieces of hard plastic which are near the surface of the water. Older turtles ate softer, translucent plastic, which look like jellyfish, from near the bottom [and closer to shore]," she said.
Research revealed the health of the water is not necessarily relevant. Turtles found near densely populated New York City showed little or no evidence of debris ingestion, while some found in pristine waters off Brisbane had swallowed debris.
"It was very difficult to trace where the plastic came from … and it had been sitting in the gut of the turtle for who knows how long," she said.
The study did not present solutions to the problem, although the researchers said they hope to raise awareness.
Schuyler said the benefits of plastic — such as being lightweight, cheap and easy to produce — are obvious, but she urged manufacturers to look at alternative technology.
There have been advances in environmentally friendly plastics, but products such as biodegradable plastic bags are not always the answer. Schuyler said such bags often end up in fragments and are eaten by older turtles.
And, researchers have found that marine life as small as plankton has ingested bits of broken-down plastic bags.
"It's not the [manufacturers'] fault the plastic ends up in the ocean. But we believe they have to utilize new technology — such as mushroom spores to create packaging material — to help the environment.
"Everybody needs to help ... we really need to look at a large-scale movement to stop debris entering the oceans."'
Schuyler said the problem with plastic in the water affects the entire marine food chain.